Monday, August 6, 2012

Can a Robot Feel A Raindrop?


Scientists One Step Closer to Developing True Artificial Skin

Engineers in South Korea have
recently released a paper on work they have been doing on flexible sensor, the high sensitivity of which rivals that of human skin. This sensor is capable of detecting a number of forces, including pressure, torsion and shear. Photo from A flexible and highly sensitive strain-gauge sensor using reversible interlocking of nanofibres by Pang, Lee, Kim, Kim, Kim, Ahn and Suh, 2012.

This new material as described in the paper by Pang, et al. represents a major scientific breakthrough in a number of ways.

First of all, the sensor is extremely sensitive to pressure; it can detect pressures as low as 5 pascals (which is about 100 to 1000x lighter than the pressure you would exert picking up a pen or pencil.) This is sensitive enough to detect a ladybug walking or a water droplet bouncing.

In addition to possessing high sensitivity to pressure, this material can also detect and quantify the effects of torsion (or twisting motions) and shear (pulling/stretching motions)--and it can do all this simultaneously. This makes the new sensor a good candidate for an artificial skin, because this material represents the first time scientists have been able to develop a sensor that can simultaneously detect all of these different forces in much the same way our own skin does. Furthermore, because it is light, flexible, and does not contain any brittle electronics like
past attempts, this new sensor could also be much more durable and potentially easier and cheaper to manufacture.

The inspiration behind this new sensor was beetles, which lock down their wings when not flying. When resting, rows and rows of tiny fibers on a beetle's wings and body interlock as a result of weak attractive forces; this holds their wings to their bodies (much like velcro.) For application as a sensor, sheets of similar hairs were manufactured from a special polymer, then coated with metal to make them electrically conductive. Finally, one sheet of fibers was layered on top of another, with the fibers interlocking. When they lock together the fibers, of course, touch--completing a circuit and allowing an amount of applied current to pass through and be measured. The degree to which the fibers touch limits the current flow, which in turn allows one to determine the magnitude of the forces applied to the sheets.

The makers of this new technology already have numerous ideas for its use. Aside from potentially allowing robots to get reliable tactile feedback about their surroundings (raindrops included), there is also potential for this material to be used in medical sensors for monitoring heart rate and/or muscle movement, or even for giving people with prosthetic limbs sensation in those areas again.

Sources/Further Reading

Electronic sensor rivals sensitivity of human skin by Katherine Bourzac
Engineers create ultra-sensitive artificial skin by Bob Yirka

Beetle Wings Inspire Electronic Sensor, Makes Machines More Sensitive Than Man by Sui Ying Teoh

~Andrew Farris

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